Not Applicable.
Not Applicable.
This invention relates generally to vessel navigation systems and more particularly to a marine navigational system for vessels that provides information including a range between the vessels and a dock or an obstacle.
As is known in the art, conventional vessels can have a primary propulsion system of two types. First, one or two propellers can be angularly fixed in a position parallel with the keel of the vessel and a rudder can be associated with each of the propellers. Alternatively, one or two propellers may be angularly movable with regard to the keel of the vessel and there may be no rudders. The term xe2x80x98secondary propulsion systemxe2x80x99 is used herein to describe any other propulsion system on the vessel. Secondary propulsion systems are known to one of ordinary skill in the art to provide manual control of thrust at angles to the keel of the vessel for tight maneuvers. For example, bow and stem thrusters are known in the art.
As is also known, a vessel may have various forms of marine navigational equipment. Exemplary marine navigational systems include global positioning systems (GPS), magnetic compasses, gyro-compasses, marine radar systems, wind speed indicator systems, water current sensor systems, and marine speed logs.
Marine radar systems typically include an antenna mounted high on the vessel to allow the radar system to detect objects at the greatest possible range from the vessel. As is known in the art, a conventional marine radar system emits a pulsed beam of radar energy from the radar antenna and receives echoes by the radar antenna as the radar energy reflects off of objects in the path of the radar beam. The time delay between the transmitted pulse and the returned echo is used by the radar system to predict a distance from the vessel to the reflecting object. Typically, the radar beam is mechanically turned or xe2x80x9csweptxe2x80x9d in the azimuthal direction and the azimuthal steering of the beam is used to predict the azimuthal angle to the object. The conventional radar beam is swept azimuthally by mechanically rotating the radar antenna.
The beam width of a conventional marine radar is relatively narrow in azimuth, approximately 5 degrees, and relatively wide in elevation, approximately twenty five degrees, so as to form a vertically oriented fan shape. As with any projected energy, the fan shaped beam spreads spherically from the antenna, causing the fan shaped beam to have an outer xe2x80x98frontxe2x80x99 edge that is curved as if to lie on a sphere that has the radar antenna at its origin.
The fan shaped azimuthally rotated beam provides sufficient range prediction accuracy for objects that are relatively far from the radar antenna. Due in part to the curved wavefront of the fan shaped beam, the conventional marine radar system range prediction accuracy is greatest at long ranges and degrades at close-in distances. Essentially, for relatively short ranges, the conventional marine radar cannot distinguish range difference between a farther tall object and a nearer short object. Both the farther tall object and the short nearer object can produce echoes with the same time delay. Thus, the conventional radar beam is not well suited for close-in docking operations. Conventional marine radars have a minimum display range that is typically hundreds of feet and display resolutions of tens of feet. For vessel docking, range accuracies and resolutions of less than plus or minus 1 foot would be desirable at vessel to dock ranges within 25 feet.
It is well known in the art that docking error can result in damage to the vessel and/or to the dock. As conditions become increasingly windy or where the water current is high, the likelihood of damage is greatest. The docking maneuver requires complex manual fore and aft thrust from the primary propulsion system or complex thrust control of the secondary propulsion system.
It would, therefore, be desirable to provide a system that provides accurate range data to the operator of a vessel when the vessel is in close proximity (e.g. 25 feet or less) to an obstacle, dock, or docking structure. It would be further desirable to provide a system that directly conveys to the operator of the vessel accurate relative velocity data corresponding to relative velocity between the vessel and an obstacle, dock, or docking structures.
In accordance with the present invention, a system for conveying navigational information to a vessel operator includes one or more radar systems coupled to a display processor for providing navigational information to the display processor, and a display coupled to the display processor for providing the navigational information to the vessel operator. The radar systems provide electronically steered conical beams to provide high accuracy measurements at close proximity to the vessel. The navigational information can include vessel to dock and vessel to obstacle range and relative velocity.
With this particular arrangement, the docking information system for boats of the present invention provides accurate close-in range and relative velocity information, corresponding to obstacles or a dock, to the operator of a vessel. With these characteristics, the docking information system for boats of the present invention. allows the vessel operator to both avoid obstacles and accurately dock the vessel. The likelihood of close-in obstacle collision is minimized. Similarly, the likelihood of manual docking error and resulting damage are minimized.